add code verifier tests

GoTrue/src/commonMain/kotlin/io/github/jan/supabase/gotrue/CodeVerifierCache.kt

@@ -28,9 +28,9 @@ interface CodeVerifierCache {
 /**
  * A [CodeVerifierCache] that uses the [AtomicRef] API.
  */
-class MemoryCodeVerifierCache: CodeVerifierCache {
+class MemoryCodeVerifierCache(codeVerifier: String? = null): CodeVerifierCache {
 
-    private var codeVerifier by atomic<String?>(null)
+    private var codeVerifier by atomic(codeVerifier)
 
     override suspend fun saveCodeVerifier(codeVerifier: String) {
         this.codeVerifier = codeVerifier

GoTrue/src/commonTest/kotlin/CodeVerifierCacheTest.kt

@@ -0,0 +1,23 @@
+import io.github.jan.supabase.gotrue.MemoryCodeVerifierCache
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+class CodeVerifierCacheTest {
+
+    @Test
+    fun testMemoryCodeVerifierCache() {
+        runTest {
+            val codeVerifier = "codeVerifier"
+            val codeVerifierCache = MemoryCodeVerifierCache(codeVerifier)
+            assertEquals(codeVerifier, codeVerifierCache.loadCodeVerifier())
+            val newCodeVerifier = "newCodeVerifier"
+            codeVerifierCache.saveCodeVerifier(newCodeVerifier)
+            assertEquals(newCodeVerifier, codeVerifierCache.loadCodeVerifier())
+            codeVerifierCache.deleteCodeVerifier()
+            assertNull(codeVerifierCache.loadCodeVerifier())
+        }
+    }
+
+}